Recently, various carbon-carbon coupling reactions using metal catalysts are reported in the field of organic chemistry. The advancement in the organometallic chemistry has enabled total synthesis of land and marine natural products of very complex structure, which had been impossible with the artificial synthesis. In particular, the carbon-carbon coupling reaction using boron, developed by Professors Suzuki and Miyaura, gives more environment-friendly and less harmful products than other reactions using zinc, tin or magnesium. Since the reaction is more stable (e.g., water is used in the reaction) and easily applicable to various fields (total synthesis of natural products, medicinal chemistry, polymer synthesis, etc.), studies are actively carried out thereabout (Chem. Rev. 1995, 95, 2457; Angew. Chem., Int. Ed. 2001, 40, 4544). Usually, the Suzuki coupling reaction is performed using a palladium (Pd) organometallic catalyst. Formerly, organoboronic acids or organoboronate esters were used as starting material. However, because the organoboronic acid or the organoboronate ester tends to form a dimer or a trimer, a quantitative reaction is difficult. In addition, there is a problem of recovering the expensive ligand such as catechol, pinacol, diethanolamine, etc., which is used to stabilize the organoboronate ester. Further, the reactants are easily attacked by a Lewis base or other common nucleophile to lead to side reactions. On the contrary, potassium organotrifluoroborates are tolerant to air and moisture, and may be prepared easily by adding inexpensive potassium hydrogen fluoride (KHF2) to the organoboronic acid or the organoboronate ester. In addition, since there is no significant difference in reactivity for the Suzuki, the carbon-carbon coupling using potassium organotrifluoroborates will be utilized in many fields (Aldrichimica Acta 2005, 38, 49; J. Org. Chem. 2003, 4313; Acc. Chem. Res. 2007, 40, 275; Tetrahedron 2007, 63, 3623).
Sigma-Aldrich, the world's leading reagent producing company, is selling more than 30 potassium organotrifluoroborates. Other dozen small- or large-sized reagent companies are also producing potassium organotrifluoroborates used in the field of combinatorial chemistry or medicinal chemistry in small quantities. These compounds are expected to replace the organoboronic acids or the organoboronate esters for the Suzuki coupling reactions. However, in spite of the potential demand, the currently available potassium organotrifluoroborates are not enough to satisfy the needs. Recently, various derivatives of potassium organotrifluoroborate and simple methods for preparing them are reported (J. Am. Chem. Soc. 2003, 125, 11148; Org. Lett. 2006, 8, 75; Org. Lett. 2006, 8, 2767; J. Am. Chem. Soc. 2006, 128, 9634; J. Org. Chem. 2006, 71, 749; J. Org. Chem. 2006, 71, 6135; Org. Lett. 2007, 9, 821; J. Org. Chem. 2007, 72, 3558). However, more researches are required.
In this regard, development of novel potassium organotrifluoroborate derivatives is important in drug developments based on synthesis of various organic products and physiologically active natural products to easily synthesize sensitive or complicated substances.
With all the usefulness, the potassium organotrifluoroborate compounds have the following drawbacks in the preparation method thereof.
(1) Usually, the potassium organotrifluoroborate compounds are prepared from relatively expensive organoboronic acids or organoboronate esters as starting material.
(2) In Scheme 1, in order to synthesize the organoboronic acid or organoboronate ester having an alcohol group, a complicated process of protecting the hydroxyl group before and the lithium-halogen exchange reaction and then removing the protecting group is required.
(3) In Scheme 1, the silyl (—SiR3) compounds used to protect the hydroxyl group are relatively expensive. Accordingly, the existing potassium organotrifluoroborate synthesis method is uneconomical.
(4) Since the organoboronic acid or organoboronate ester compound in Scheme 1 tends to form a polymer easily in the air, there are problems in purification, storage and quantitative reaction.

Accordingly, a simple, inexpensive and fast method for preparing a potassium organotrifluoroborate having a hydroxyl group is needed.